1. Field of the Invention
The present invention relates to an apparatus for manufacturing an electron source, a method for manufacturing an electron source, and a method for manufacturing an image-forming apparatus. More particularly, the invention concerns a planar image-forming apparatus.
2. Description of the Related Art
The operation of a surface conduction electron-emitting element is based on a phenomenon wherein electron emission occurs when a current flows through a thin, small film formed on a substrate, parallel with the film surface. The present applicant has made many suggestions regarding surface conduction electron-emitting elements having novel structures, and the applications thereof. The basic structure and manufacturing methods of surface conduction electron-emitting elements are disclosed, for example, in Japanese Patent Laid-Open Nos. 7-235255 and 8-171849.
A typical surface conduction electron-emitting element includes a pair of element electrodes opposed to each other on a substrate, and a conductive thin film which is connected to the pair of element electrodes and which is provided with an electron-emitting section. A crack is made in a part of the conductive thin film. A film containing at least one of carbon and a carbon compound as a principal constituent is formed at the edge of the crack.
By placing a plurality of such electron-emitting elements on a substrate and by joining the individual electron-emitting elements by wiring, an electron source provided with a plurality of surface conduction electron-emitting elements is manufactured. By combining the electron source and a phosphor layer, a display panel of an image-forming apparatuses manufactured.
Examples of conventional methods for manufacturing such a panel using the electron source will be described below.
In a first manufacturing method, first, an electron source substrate is fabricated, in which a plurality of elements formed on a substrate is joined by wiring, each element including a conductive film and a pair of element electrodes connected to the conductive film. The entire electron source substrate is placed in a vacuum chamber. After the vacuum chamber is evacuated, a crack is formed in the conductive film of each element using an external terminal. A gas containing an organic substance is introduced into the vacuum chamber, and a voltage is applied again through the external terminal to each element in an atmosphere containing the organic substance so that carbon or a carbon compound is deposited in the vicinity of the crack.
In a second manufacturing method, first, an electron source substrate is fabricated in which a plurality of elements formed on a substrate is joined by wiring, each element including a conductive film and a pair of element electrodes connected to the conductive film. Next, the electron source substrate and a substrate provided with a phosphor layer are joined to each other with a supporting frame therebetween to produce a panel of an image-forming apparatus. Next, a voltage is applied to the conductive film of each element through an external terminal to form a crack in the conductive film. A gas containing an organic substance is introduced into the panel space via an exhaust pipe of the panel and a voltage is applied again through the external terminal to each element in an atmosphere containing the organic substance so that carbon or a carbon compound is deposited in the vicinity of the crack.
In the first manufacturing method described above, in particular, as the size of the electron source substrate increases, a larger vacuum chamber and a high vacuum exhauster are required. In the second manufacturing method, it takes a long time to evacuate the panel space of the image-forming apparatus and to introduce the gas containing the organic substance into the panel space.
Moreover, in the manufacturing methods described above, an activation gas is consumed in the activation process in order to deposit the carbon or the carbon compound on the conductive films including electron-emitting sections Therefore, when the relationship between the consumption of the activation gas during activation and the flow of the activation gas in the panel or chamber is inappropriate, the activation gas partial pressure in the panel decreases over time during the activation process. If the pressure of the activation gas changes in the activation process, the characteristics of the electron-emitting elements after activation become irregular. Specifically, since the activation rate and the electron emission efficiency depend on the pressure of the activation gas, the luminance of the panel is irregular.
FIG. 13 is a graph illustrating the relationship between the activation gas partial pressure and the electron emission efficiency. The activation gas partial pressure in the horizontal axis is shown on a logarithmic scale. The measurements performed by the present inventors show that, if the activation gas partial pressure becomes 0.8 times the original partial pressure, the electron emission efficiency becomes 1.1 times the original efficiency. Therefore, the electron emission efficiency varies depending on the sequence of activation. As a result, variations in luminance exceed several percent, and the product does not exhibit satisfactory performance.
On the other hand, if the flow of the activation gas is too large, the range of partial pressure distribution in the vacuum chamber increases and the difference between the partial pressure in the vicinity of the gas inlet and the partial pressure in the vicinity of the gas outlet increases, resulting in irregular luminance, the same problem encountered when the activation gas partial pressure changes over time.
The objects of the present invention are to provide an apparatus for manufacturing an electron source having a superior electron emission characteristic and luminance uniformity at an improved manufacturing rate, with improved mass productivity, to provide a method for manufacturing the electron source, and to provide an image-forming apparatus using the electron source.
In one aspect of the present invention, in a method for manufacturing an electron source including an electron-emitting element having a first electrode, a second electrode, and a carbon film disposed between the first electrode and the second electrode, the-electron-emitting element being placed on a front surface of a substrate, the method includes the steps of covering a partial front surface or the entire front surface of the substrate provided with the first electrode and the second electrode by a container; introducing a gas composed of a carbon compound into the container via a gas inlet of the container; and forming the carbon film by applying a voltage between the first electrode and the second electrode, wherein the relationship 1/(4/Cxxe2x88x921/Cz)xe2x89xa7Soutxe2x89xa74Sactxe2x88x92Cin is satisfied, where Cin is the conductance from the gas inlet to the position of the substrate nearest to the gas inlet, Cx is the conductance from the position of the substrate nearest to the gas inlet to the position of the substrate nearest to a gas outlet for evacuating the container, Sout is the effective exhaust rate of an exhaust unit connected to the gas outlet, Sact is the consumption rate of the gas consumed by applying the voltage to the electron-emitting element, and Cz is the conductance from the substrate to the gas outlet.
In the method for manufacturing the electron source, preferably, the electron source includes a plurality of electron-emitting elements, and the relationship 1/(4/Cxxe2x88x921/Cz)xe2x89xa7Soutxe2x89xa74xc2x7nxc2x7Sact1xe2x88x92Cin is satisfied, where Sact1 is the consumption rate of the gas for each element, and n is the number of elements simultaneously subjected to the step of forming the carbon film.
In the method for manufacturing the electron source, preferably, the electron source includes a plurality of electron-emitting elements, a plurality of X-direction lines for commonly connecting a plurality of first electrodes, and a plurality of Y-direction lines for commonly connecting a plurality of second electrodes, and in the step of forming the carbon film, the voltage is applied between each first electrode and each second electrode through the X-direction line and/or the Y-direction line.
In the method for manufacturing the electron source, preferably, in the step of forming the carbon film, the carbon film is simultaneously formed on the elements connected to some of the X-direction lines adjacent to each other.
In the method for manufacturing the electron source, preferably, in the step of forming the carbon film, the carbon film is simultaneously formed on the elements connected to some of the X-direction lines nonadjacent to each other.
In another aspect of the present invention, in a method for manufacturing an image-forming apparatus, the image forming apparatus including: an electron source including an electron-emitting element having a first electrode, a second electrode, and a carbon film disposed between the first electrode and the second electrode, the electron-emitting element being placed on a front surface of a substrate; and an image-forming member facing the electron source and forming an image by electrons emitted from the electron-emitting element, the method includes the steps of covering a partial front surface or the entire front surface of the substrate provided with the first electrode and the second electrode by a container; introducing a gas composed of a carbon compound into the container via a gas inlet of the container; and forming the carbon film by applying a voltage between the first electrode and the second electrode, wherein the relationship 1/(4/Cxxe2x88x921/Cz)xe2x89xa7Sout4Sactxe2x88x92Cin is satisfied, where Cin is the conductance from the gas inlet to the position of the substrate nearest to the gas inlet, Cx is the conductance from the position of the substrate nearest to the gas inlet to the position of the substrate nearest to a gas outlet for evacuating the container, Sout is the effective exhaust rate of an exhaust unit connected to the gas outlet, Sact is the consumption rate of the gas consumed by applying the voltage to the electron-emitting element, and Cz is the conductance from the substrate to the gas outlet.
In the method for manufacturing the image-forming apparatus, preferably, the electron source includes a plurality of electron-emitting elements, and the relationship 1/(4/Cxxe2x88x921/Cz)xe2x89xa7Soutxe2x89xa74xc2x7nxc2x7Sact1xe2x88x92Cin is satisfied, where Sact1 is the consumption rate of the gas for each element, and n is the number of elements simultaneously subjected to the step of forming the carbon film.
In the method for manufacturing the image-forming apparatus, preferably, the electron source includes a plurality of electron-emitting elements, a plurality of X-direction lines for commonly connecting a plurality of first electrodes, and a plurality of Y-direction lines for commonly connecting a plurality of second electrodes, and in the step of forming the carbon film, the voltage is applied between each first electrode and each second electrode through the X-direction line and/or the Y-direction line.
In the method for manufacturing the image-forming apparatus, preferably, in the step of forming the carbon film, the carbon film is simultaneously formed on the elements connected to some of the X-direction lines adjacent to each other.
In the method for manufacturing the image-forming apparatus, preferably, in the step of forming the carbon film, the carbon film is simultaneously formed on the elements connected to some of the X-direction lines nonadjacent to each other.
In another aspect of the present invention, in an apparatus for manufacturing an electron source, the electron source including an electron-emitting element having a first electrode, a second electrode, and a carbon film disposed between the first electrode and the second electrode, the electron-emitting element being placed on a front surface of a substrate, the apparatus includes: a base for supporting the substrate preliminarily provided with the first electrode and the second electrode; a container for covering the front surface of the substrate supported by the base; and a voltage-applying unit, wherein, in the steps of covering a partial front surface or the entire front surface of the substrate provided with the first electrode and the second electrode by the container; introducing a gas composed of a carbon compound into the container via a gas inlet of the container: and forming the carbon film by applying a voltage between the first electrode and the second electrode using the voltage-applying unit, the relationship 1/(4/Cxxe2x88x921/Cz)xe2x89xa7Soutxe2x89xa74Sactxe2x88x92Cin is satisfied, where Cin is the conductance from the gas inlet to the position of the substrate nearest to the gas inlet, Cx is the conductance from the position of the substrate nearest to the gas inlet to the position of the substrate nearest to a gas outlet for evacuating the container, Sout is the effective exhaust rate of an exhaust unit connected to the gas outlet, Sact is the consumption rate of the gas consumed by applying the voltage to the electron-emitting element, and Cz is the conductance from the substrate to the gas outlet.
In the apparatus for manufacturing the electron source, preferably, the electron source includes a plurality of electron-emitting elements, and the relationship 1/(4/Cxxe2x88x921/Cz)xe2x89xa7Soutxe2x89xa74xc2x7nxc2x7Sact1xe2x88x92Cin is satisfied, where Sact1 is the consumption rate of the gas for each element, and n is the number of elements simultaneously subjected to the step of forming the carbon film.
In the apparatus for manufacturing the electron source, preferably, the electron source includes a plurality of electron-emitting elements, a plurality of X-direction lines for commonly connecting a plurality of first electrodes, and a plurality of Y-direction lines for commonly connecting a plurality of second electrodes, and in the step of forming the carbon film, the voltage is applied between each first electrode and each second electrode through the X-direction line and/or the Y-direction line.
In the apparatus for manufacturing the electron source, preferably, in the step of forming the carbon film, the carbon film is simultaneously formed on the elements connected to some of the X-direction lines adjacent to each other.
In the apparatus for manufacturing the electron source, preferably, in the step of forming the carbon film, the carbon film is simultaneously formed on the elements connected to some of the X-direction lines nonadjacent to each other.
As described above, in accordance with the present invention, an apparatus for manufacturing an electron source includes a base for supporting a substrate preliminarily provided with a conductor (a first electrode and a second electrode), and a container for covering the substrate supported by the base. The container covers the surface of the substrate partially, and thus it is possible to form an airtight space on the substrate with the lines connected to the conductor formed on the substrate being partially exposed to the outside of the container. The container is also provided with a gas inlet and a gas outlet. The inlet and the outlet are connected to a unit for introducing a gas to the container and a unit for discharging a gas from the container, respectively. Thereby, the atmosphere inside the container can be controlled to achieve desired conditions. The substrate preliminarily provided with the conductor is a substrate in which an electron-emitting section is formed in the conductor by an electrical process to produce an electron source. Therefore, the manufacturing apparatus of the present invention further includes a unit for performing the electrical process, for example, a unit for applying a voltage to the conductor. In such a manufacturing apparatus, reduction in size is achieved; operations, such as making an electrical connection to a power source during the electrical process, can be facilitated; and there is further freedom with regard to the design for the size and shape of the container so that introduction of the gas into the container and discharge of the gas from the container can be performed quickly.
As described above, in accordance with the present invention, in a method for manufacturing an electron source, first, a substrate on which a conductor and lines connected to the conductor are preliminarily formed is placed on a base, and the conductor on the substrate is covered by a container, excluding parts of the lines. Thus, the conductor is placed in an airtight space formed on the substrate with the lines formed on the substrate being partially exposed to the outside of the container. Next, the atmosphere in the container is controlled to achieve desired conditions, and an electrical process is performed on the conductor via the parts of the lines exposed to the outside of the container, for example, a voltage is applied to the conductor. The desired atmosphere is, for example, a reduced-pressure atmosphere or an atmosphere in which a predetermined gas is present. The electrical process is a process in which an electron-emitting section is formed in the conductor to produce an electron source. The electrical process may be performed a plurality of times in different atmospheres. For example, after the conductor on the substrate is covered by the container, excluding parts of the lines, the electrical process is performed in a first atmosphere, and then the electrical process is performed in a second atmosphere. A satisfactory electron-emitting section is thereby formed in the conductor and an electron source is produced. As will be described below, the first atmosphere is a reduced-pressure atmosphere, and the second atmosphere is an atmosphere in which a gas composed of a carbon compound or the like is present.
When the electrical process is performed in the second atmosphere, such as in a gas of a carbon compound, in order to suppress the change of the partial pressure of the gas in the vacuum container over time and in order to suppress the range of partial pressure distribution in the vicinity of the electron-emitting element, the following measures are taken. That is, it is possible to limit the amount of the reduction in the average partial pressure to 20% or less and to limit the range of partial pressure distribution in the image region to 20% or less, by setting the conditions so as to satisfy the relationship 1/(4/Cxxe2x88x921/Cz)xe2x89xa7Soutxe2x89xa74Sactxe2x88x92Cin, where Sout is the effective exhaust rate which corresponds to the combined conductance of the exhaust side conductance of a manufacturing apparatus and the exhaust rate of a pump, for example, as shown in FIG. 10, Sact is the consumption rate of an activation gas during activation, Cin is the conductance from the gas inlet to the position of the substrate nearest to the gas inlet, Cx is the conductance from the position of the substrate nearest to the gas inlet to the position of the substrate nearest to a gas outlet, and Cz is the conductance from the substrate to the gas outlet.
In such a manufacturing method, operations, such as making an electrical connection to a power source during the electrical process, can be facilitated. Since there is further freedom with regard to the design for the size and shape of the container. etc., introduction of a gas into the container and discharge of a gas from the container can be performed quickly, thereby improving the manufacturing rate as well as improving consistency in the electron emission of the electron sources manufactured, in particular, improving uniformity of the electron emission of an electron source having a plurality of electron-emitting sections.
When the electrical process is performed in a gas composed of a carbon compound, since it is possible to limit the amount of the reduction in the average partial pressure in the container to 20% or less and to limit the range of partial pressure distribution in the image area to 20% or less, the range of the variation in luminance can be set to be within several percent.
Further objects, features and advantages of the present invention will become apparent from the following description of the preferred embodiments with reference to the attached drawings.